Conventionally, techniques for waterproofing the interior of a unit in which a circuit is accommodated are known. According to the technique described in JP 2004-31416A, a power circuit section disposed on a heat dissipation member via an insulating layer is covered by a waterproof case, and the waterproof case is provided with a hood for each connector for connection to the outside. A waterproofing portion filled with an epoxy resin is formed around the external connection terminal inside the hood, and the waterproofing portion prevents water from entering the waterproof case along the external connection terminal.